Oidium is a disease that occurs due to a fungus called Uncinula necator Burr, which, although it comes from North America, is quite widespread around all of Spain.
As with all fungi, if the environment and climate are conducive to their development, it is possible that they may occur in certain sensitive varieties , even the complete loss of the harvest, and unlike mildew, Oidium requires high temperatures, a dry environment free from any humidity or cool nights.
- 1 How is powdery mildew preserved in the vineyard?
- 2 What are the symptoms and damage caused by Oidium?
- 3 Ways to eliminate Oidium
How is powdery mildew preserved in the vineyard?
Oidium can be preserved in 2 ways , which are:
In the state of mycelium inside the shoots.
In a state of peritheca , as resistant organs and on the surface of the shoots.
During spring, the fungus penetrates the shoots from contaminated shoots . The mycelium filaments develop in the green organs, which they contaminate through haustoria. If the environmental setting is conducive, the mycelium emits conidia , which develop on top of healthy organs and are located near those contaminated organs, causing them to germinate and allowing the disease to spread.
What are the symptoms and damage caused by Oidium?
The fungus that causes Oidium affects each of the green organs of the vine , however, it commonly affects the shoots, shoots and clusters more frequently.
The symptoms and damage that Oidium generally causes are:
It is possible to perceive an ash-white powder on the back and on the upper part of the leaf, which could end up covering it completely and under the powder some necrotic dots can be observed. In some cases, at the beginning of the attack, some small spots that look like oil can be seen on the upper surface, accompanied by some dark spots.
When it comes to acute attacks, the leaves appear contracted or curved and totally covered by the dust on the upper and lower sides of the leaves.
On shoots and shoots
The symptoms of Oidium usually appear as small fuzzy dark green spots, which increase in size and turn brown as the vegetation blooms and then turn black when the shoot lignifies.
At the beginning of the disease, the grains turn a leaden tone and after a while, they are completely covered by the grayish dust that is made up of the organs of multiplication of the fungus, known as comidia, under which they are usually found. some necrotic tissues of a darker shade .
The most important damage caused by Oidium is generally found in the bunches, because the intense attacks cause the development of the skin to stop and consequently the skin and the fruit of the vine crack.
Ways to remove Oidium
It is necessary to use green pruning in order to increase aeration, since in this way it is possible to form an unfavorable atmosphere for the development of the fungus and also, it allows the fungicides to penetrate the soil , being the only possible way to eliminate the fungus that causes Oidium.
In the same way , there are a large number of products and control strategies that are of great help when it comes to eliminating Oidium through chemical products and one of the most used products in this case is powdered sulfur , which if placed in the right way and time is quite effective in eliminating the fungus.
The best way to do this is to apply it during the spring when the temperature is above 18ºC and during the summer when it does not exceed 35ºC.